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Candela (millicandela) to Lumen Conversion Wizard

Luminous Intensity (millicandelas)
Beam Angle (degrees)

The purpose of this calculator is to provide lighting professionals and installers a realistic approximation in converting millicandelas (also known as candelas) to lumens for the purposes of selecting the appropriate LED light to fit an application. Of particular interest to most users of this calculator is its usefulness in comparing the light output of various LEDs with different beam angles. In order for this calculator to work properly the beam angle must be known.

The math behind the wizard is pretty straightforward. It takes the beam angle given by the user and converts it into a solid angle in units of steradians. It then applies this information into the formula of 1 candela = 1 lumen/steradian in order to complete the conversion.

It should be noted that this calculator can only give a close approximation and not a guaranteed exact conversion. This is due to several factors, the most important being the often unclear measurement method for luminous intensity due to its omittance by most manufacturers. This information is omitted because manufacturers almost always list their luminous intensity specifications in the most favorable way possible, regardless of the actual measurement method used. In fact, there is no industry standard for measuring luminous intensity - allowing manufacturers to come up with their own “standards of measurement”. This makes it incredibly tempting for manufacturers to push their numbers into the maximum possible range instead of realistic luminous ranges seen in normal operating conditions.

Considering this, the wizard operates on the assumption that the luminous intensity value supplied is actually an average value across the entire beam angle and not an exact number. The problem surrounding this is further compounded with wide angle LEDs such as auxiliary crane lights, which will likely face the most distortion out of all different types of LEDs in this calculator.